CROSS-REFERENCE TO RELATED APPLICATION
This application is related to a copending U.S. patent application Ser. No. 12/558,223 filed Sep. 11, 2009 and entitled “VARIABLE POWER SOURCE AND RELATED POWER SUPPLY METHOD,” and which has the same assignees as the present application. The disclosure of the above-identified application is incorporated herein by reference.
BACKGROUND
1. Technical Field
The present disclosure relates to power sources and, particularly, to a power source system capable of continuously adjusting an output thereof to meet the requirements of a variable load.
2. Description of Related Art
Current electric systems typically include a power source, a driving circuit, and a load. The load may consume different amounts of power at different times. In such case, the driving circuit is configured for altering an output of the power source to meet the requirements of the load. For example, the driving circuit may include an inverter for converting a direct current flowing out from the power source into an alternate current, and/or a transformer for adjusting an output voltage of the power source. In such an electric system, a great amount of power may be lost in the driving circuit itself when the driving circuit provides power for the load. Thus, the voltage provided to the load may be reduced, and accordingly the adjustment of the power provided to the load may not be precise.
Therefore, it is desirable to provide a power source system which can overcome the above-mentioned problems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a power source system of an exemplary embodiment of the present disclosure, together with a load.
FIG. 2 is a schematic view of a power source of the power source system of FIG. 1, together with the load.
DETAILED DESCRIPTION
Referring to FIG. 1, a power source system 100, according to an exemplary embodiment, is shown. The power source system 100 is configured for supplying power for a load 300. The power source system 100 includes a power source 20, a voltage fine adjusting unit 22, and a controller 24. The load 300 has a resistance R. The rated voltage and rated flow of electrical current of the load 300 are represented as V and I respectively.
The power source 20 is configured for storing electric energy and providing electric energy to the load 300. In particular, the power source 20 includes a number of cells 200, a number of positive switches 202 b, a number of negative switches 204 b, a number of serializing switches 206 b, a positive output 202 a, and a negative output 204 a. In this embodiment, the number of cells 200 is N, the number of positive switches 202 b is N, the number of negative switches 204 b is N, and the number of serializing switches 206 b is N, wherein N is a natural number.
The cells 200 can be dry batteries, rechargeable batteries or solar batteries. Each of the cells 200 includes a positive electrode 200 a and a negative electrode 200 b. An electromotive force ε of the cells 200 is typically fixed.
The positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b can be, among other types, push-button switches, thin film switches, toggle switches, mercury tilt switches, lever switches, micro switches, or travel switches. In this embodiment, all the positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b are integrated into a grammed switch.
In assembly, the cells 200 are arranged in parallel. Each of the positive switches 202 b connects a positive electrode 200 a of a corresponding cell 200 to the positive output 202 a. Each of the negative switches 204 b connects a negative electrode 200 b of a corresponding cell 200 to the negative output 204 a. Each of the serializing switches 206 b connects a negative electrode 200 b of a corresponding cell 200 to a positive electrode 200 a of an adjacent cell 200.
The controller 24 is configured for controlling the output of the power source 20 by selectively turning on and turning off the positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b. The controller 24 includes a setting unit 240, a detecting unit 242, and an adjusting unit 244.
The setting unit 240 is configured for selectively turning on and turning off the positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b to control an output voltage of the power source 20 before starting supplying power to the load 300. In particular, a serializing number N1 and a parallelizing number N2 are calculated by the setting unit 240 using, for example, the following two formulas: (1): N1=[V/ε]; and (2): N2=[IR/ε−N]; wherein [V/ε] represents rounding off V/ε, and [IR/ε−N] represents rounding off (IR/ε−N). In the present embodiment, unless the context indicates otherwise, rounding off means simplifying a number with a decimal point to the nearest integer. In more detail, the setting unit 240 stores the electromotive force ε and the total number N of the cells 200. As such, once the resistance R, the rated voltage V, and the rated flow of electrical current I of the load 300 are inputted to the setting unit 240, the serializing number N1 and the parallelizing number N2 can be determined by the setting unit 240. Furthermore, the setting unit 240 can control the positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b by controlling the grammed switch to connect N1+1 of the cells 200 in series between the positive output 202 a and the negative output 204 a by switching on N1 of the serializing switches 206 b, and, except for the N+1 serialized cells 200, by controlling the grammed switch to connect N2 of the cells 200 in parallel between the positive output 202 a and the negative output 204 a by switching on N2 of the positive switches 202 b and N2 of the negative switches 204 b of the N2 cells.
It should be understood that (N1+N2+1) should be less than N. Otherwise, the power source 20 cannot supply power for the load 300. Based upon the formula (1), it can be determined that a theoretical output voltage VOT of the power source 2000 is about (N1+1)ε, which is, in theory, equal to or slightly higher than the rated voltage V of the load 300. Based upon both the formulas (1) and (2), it can be inferred that a theoretical flow of electrical current IOT through the load 300 is about (N1+N2+1)ε/R , which is, in theory, equal to or slightly higher than the rated flow of electrical current I of the load 300. Thus the setting unit 240 is able to control the grammed switch such that both the rated voltage V and the rated flow of electrical current I of the load 300 can be satisfied. However, due to incremental exhausting of electric power of the cells 200 and incremental increasing of internal resistances of the cells 200, a real output voltage VOR and a real flow of electrical current IOR tend to deviate from the theoretical output voltage VOT and the theoretical flow of electrical current IOR, respectively. Therefore, the detecting unit 242 and the adjusting unit 244 are employed to reduce or eliminate any such deviation.
The detecting unit 242 is configured for continuously measuring differences between the real output voltage VOR and the rated voltage V of the load 300, and differences between the real flow of electrical current IOR and the rated flow of electrical current I of the load 300.
The adjusting unit 244 is configured for continuously adjusting the output voltage VOR and the real flow of electrical current IOR by adjusting on/off states of the positive switches 202 b, the negative switches 204 b, and the serializing switches 206 b, based upon the differences measured by the detecting unit 242.
As such, the real output voltage VOR can be coarsely maintained around the rated voltage V of the load 300. The real flow of electrical current IOR can be coarsely maintained around the rated flow of electrical current I of the load 300. This is because each of the real output voltage VOR and the real flow of electrical current IOR can only be adjusted incrementally (each increment is ε and ε/R, respectively). Therefore, the real output voltage VOR and the real flow of electrical current IOR may need further fine adjustments to exactly meet the requirements of the load 300.
The voltage fine adjusting unit 22 is configured for precisely adjusting the real output voltage VOR and the real flow of electrical current IOR. In particular, the voltage fine adjusting unit 22 includes a judging sub-unit 220 and a precise transformer 222. The judging sub-unit 220 judges whether differences between the real output voltage VOR and the rated voltage of the load 300 are within acceptable levels, and whether differences between the real flow of electrical current IOR and the rated flow of electrical current of the load 300 are within acceptable levels. If the determination is “yes” for both judgments (i.e., both within acceptable levels), the judging unit 220 directly passes the output of the power source 20 to the load 300. If the determination is “no” for either or both judgments (i.e., either or both not within acceptable levels), the judging unit 220 passes the output of the power source 20 to the precise transformer 222 for precise voltage adjustment, so that the output of the precise transformer 222 exactly meets the requirements of the load 300.
While various exemplary and preferred embodiments have been described, it is to be understood that the disclosure is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art) are intended to also be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.